Magnetic control system



Feb. 16, 1932. w. B. COOLEY MAGNETIC CONTROL SYSTEM Filed Spt. 3, 1929 2 Sheets-Sheet il'am ,B

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Feb. 16, 1932. w a, COOLEY MAGNETIC CONTROL SYSTEM Filed Sept. 3, 1929 2 Sheets-Sheet 2 .I Ubl- 11%;

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%I fa e Patented Feb. 16, 1932 UNITED STATES PATENT OFFICE WILLIAM B. COOLEY, OF MILWAUKEE, WISCONSIN, ASSIGNOR TO HEVI DUTY ELECTRIC COMPANY, OF MILWAUKEE, WISCOHSIN, A COBPOB ATION OF 'WISCONSIN MAGNETIC CONTBOL SYSTEM Application filed September 3, 1929. Serial No. 390.182.

My invention relates broadly to heat treatment furnaces and more particularly to a system for determining the condition of the i cent and recalescent points of the steel. I

utilize this relationship in attaining the objects of my invention.

One of the objects of my invention is to provide a system 'for electrically determining the time at which magnetizable material 'treated in a heat treatment chamber may -reach a condition or reference point, from which subsequent Operations can be determined, and where the electrically determining means is operatively independent of the source of heat which may be supplied to the heat treatment chamber.

Another object of my invention is to provide a magnetic system positioned adjacent material which is subjected to heat 'treatment in a heat treatment furnace, for determining the condition of the material under heat treatment operatively independent of 'the heat source which is applied to the furnace.

Still another object of my invention is to provide a magnetic system disposed adjacent material in a furnace for determining the condition of` material which is subjected to heat treatment, the magnetic' system being entirely independent of the heating means which is supplied to the furnace.

A further object of my invention is to provide a magnetic system inductively related to material in a furnace for determining the condition of material which is being subjected to heat treatment, and in combination therewith, but separate from the magnetic system, 'another system for automatically controlling the temperature of the furnace without affecting the magnetic system.

A still further object of my invention is to provide a magnetic system for controlling the time period over w ich material within the furnace is subjected to heat treatment in accordance with the condition of the material within the furnace and independently of means by which the material in the furnace may be heated.

Other and further objects of my nventi on will be understood from the specification hereinafter following by reference to the accomp'anying drawings, in which:

Figure 1 is a cross-sectional View through a heat treatment furnace showing the magnetic indicatoi` system of my invention; Fig. 2 is a View showing-a modified form of magnetic indicator system embodying the principles of m invention; Fig. 3 illustrates a. further mo ified form of electrical indicator apparatus which may be em loyed in the system of my invention; and ig. 4: illustrates still another method of applying the electrical indcator system to heat treatment furnaces embodying the principles of my invention.

My invention is directed to a magnetic indicator and control system for heat treatment furnaces, wherein the point at which the steel or other magnetizable metal under heat treatment changes its magnetic properties upon heating, may be detected so that heating may be dscontinued, or the temperature modified, or the steel withdrawn, or permitted to remain in the furnace for definite subsequent periods at the discretion of the operator. My invention makes use of the principle that steel or other magnetizable metal changes its magnetic properties when heated to' certain temperature, depending upon the analysis of the steel. This change of magnetic properties, occurring at a positive transformation or critical point in the steel, establishes when known, ,a reference point in the heat treatment; My 'invention provides for magnetically determining the point at which the steel or other metal under heat treatment changes its magnetic properties, or has reached a definite transformation point, so that the proper heat treatment can be determined, the magnetic determining means Operating independently of the heatn source.

n the system of my invention, a heat treatment fumace is provided with any form ondar system which is magnetically coupled, may provide a single winding surrounding the heat treatment chamber and apply to the indicator er control apparatus, potential difi'erences which exist across any se lected number of turns and afiected by the change in potential of the circuit due to the influence of the material under hoat treatment within the chamber, I may provide an indicator apparatus which is highly sensitive by reason of the independent energizetion of separate windin of the indcator apparat'us bein ener 'ze from difierent positons along t e coi s which surround the material in the heat treatment chamber,

In other furnaces l may provide a magnetic circuit magnetically related to the heat treatment chamber in which the air gap, thus included, is changed by the introduction intothe air ga ofmagnetizable material to be heat treate thereby changing the magnetic conditions. Predetermined magnetizing force may be supplied to the magnetic circuit and the change in magnetic conditions, or the critical transformation points of the material to' be heat treated, may be detected by an indicator and .thereby the character of subsequent heat treatment to be given material within the chamber may be determined.

Referring to the drawings, in Fig. 1 reference character 1 designates a furnace structure which encloses a heat treatment chamber 2 in which the steel or other magnetizable metal 3 is placed. Any form of heating source -may be applied to the furnace and for the purpose of illustrating my invention, I have shown a' resistor et disposed within the furnace and electrically connected to a supplysource 36 connected to line 5 through magnetic switches 6. l`he closing and opening of magnetic'switches 6"is controlled by a relay 7 which is actuated by pyrometer 8 in accordance with the temperature in the heat treatment furn'ace, cutting on or o the heating energ'yto the resistor 4. As heretofore pointed out any form of heating source may e applied to'the 'heat treatment chamber in so fares my present' invention is concerned, as my invntion is applicable to all forms of hoat treatment furnaces independent of the character of the beat source. A primary coil 9 is' shown` surrounding the furnace chameasner ber 1, the primary coil 9 being in inductive relation to the secondary coil 10 where the coils are insulated b means of insulation member 11. I provide a com ensator 12 which includes -secondary win n 14 and primary winding 15 inductivel re ated 'one to the other, the primary win ing 15 being connected in series with the primary coil 9 while the secondary winding 14 is connected in series with the secondary coil 10.- An indicating apparatus such as galvanometer 16 is connected in series with the secondary winding 14 and secondarv 10, and is responsive to voltages in secondary coil 10 to indi- Cate the magnetic condition of the material 3 within the beat treatment chamber 2. The galvanometer 16 by having Contacts, not shown, may actuate a pilot light, an alarn bell, or other form of indicator. The potential supplied at terminals 19 energizes primar winding 9, and the magnetic field which is t us established permeates the steel or magnetizable metal charge 3 which is under hcat treatment. p

lBy the proper adjustment of the compensator which includes movable core member'.

17, 'alvanometer 16 may be defiected to a preetermined or zero condition indicat'ing a position of balance of the ma netic fiux through the furnace chamber without the char e 3 in position therein. Upon introducton of the charge 3, the galvanometer 01' indicator 16 is deflected by virtue of the increased fiux which passes through the furnace chamber in the path partially closed by the steel or magnetizable charge 3. Under conditions of continued heat treatment, the.

charge 3 changes its magnetic properties and when that transformation point is reached, the heated cycle can be concluded or can be determined by the artan ement illustrated in Fig. 1. The operator y noting the change of magnetic properties of the charge 3 by reading the galvanometer or indicator 16, can cut oii' the supply of heating energy from the circuit 5, by any suitable means such as the customary switch, or he may elect to soak the charge :for any subsequent time.

In Fig. 2, I have illustrated a single winding 18 across which magnetizi'ng potential is supplied at terminals 20 for establishin a magnetic flux through the charge 3 wit in the furnaoe. The difference of potential along the winding 18 may be observed by the connection of galvanometer or indicator 16 through the selected turns indicated at 21. This arrngement serves as an auto-transformer where a selected potential variable in accordance with the magnetic condition of the charge 3 is suppliedto the indicator 16.

In Fig. 3, I have shown the winding ls having different sections of its turns connected to the windings of a power factor meter 22. Winding 23 of the power factor meter 22 connects to selected turns 'of the winding 18 characters used to describe the temperature control equipment in Fig. l-have been used such as designated at 25, while winding 24:

of power factor meter 22 connects to section'26 of the winding 18. Relative movement of windings 23 and 24 operates indica- 5 tor 27 for enablin the magnetic condition of the charge 3 wit in the furnace to be observed.

In Fig. 4, I have shown the principles of my invention applied to a comparatively large size furnace designated at 28 having a charge 29 disposed therein. A magnetic circuit indicated at 30 is formed around the furnace terminating in pole pieces 31 and 32 which may establish a magnetic field through the furnace chamber 33 and the charge 29 located therein. A magnetic winding 34: is provided to establish a permanent field through the furnace chamber 33, and has in series the primary 15 of a compensator 12 the charge 29 being aligned with the path oi the magnetic lines of force. While means heretofore described for establishin a flux may be employed, I have found that t e positive magnetic circuit 30 may increase the strength of the magnetic field in the air ap, especially in large furnaces, and reners the variation of such field due to changes in the magnetic conditions of the charge 29, observable with greater accuracy. By means 0 of secondary winding 35 which is disposed on pole piece 31 and connected in series tothe secondary 14 of a compensator 12, energy may be supplied to an indicator 16. Compensator 12 has an' adjustable core 17 for balancin purposes as described under Fig. 1. The e fect by the charge, and subsequent determination is the same as under Fig. 1. The same form of temperature control ap aratus is employed in the modified form o furnace as is -illustratdin Fig. ;1 and the same reference to designate corresponding parts in the temperature control apparatus shown in Fig. 4.

While I have described my invention in certain of'its preferred embodinents, I desire that it be understood that modifications maybe made and that no limitations upon my invention are intended other than are imposed by the scope of the appended claims."

What I claim as new and desire to secure by Letters Patent of the United States is as follows: v

1. In combination, a furnace having a heatthe said chamber, a source of electric energy,

` a coil enclosing said chamber connected to said first coil, and means responsive to change ing chamber, work to be heated located in.

in the inductive effects of the first coil and connected in series with said second coil.

2. In a furnace, a heat treatment chamber for housing and subjecting a charge of magnetizable material to a heat treatment, a par of coils surrounding said chamber, means coupling said coils one to the other, a source of potential for supplying electrical energy to one of said coils through said coupling means, indicating means ;connected to the other of said coils, and electrical means indepcndent of said coils for su plying heat to the magnetizable charge wit in said chamber, said indicating means being controlled directl in accordance with the pro erties of said magnetizable charge under t e action of heat treatment from said electrical means.

3. In a furnace, a heat treatment chamber for receivin a char e of magnetizable material, means ?or supp yingheat to said charge within said heat treatment chamber, a pair of coils surrounding said chamber, one of said coils being energized to excite the other of said coils for producing a nagnetic flux through said magnetizable charge heating elements in said chamber, an in ependent power supply circuit for energizing said heating elements, means in circut with' said last mentioned coil for indicatin the magnitude of flux passing through sai charge for determining the change in magnetc properties of said charge in accordance wth the heat treatment to which said charge is subjected. i

4. In a furnace a heat treatment chamber arranged to receive a charge of magnetizable material, means for subjecting said magnetizable material to heat, independent means for subjecting said charge'to magnetic fiux and means controlled by the magnitude of the magnetic flux passing through said charge for indicating the ma netic condition of the charge under the varia le effects of heat treatmentthereof. 4

5. In a heat treatment furnace, a heat treatment chamber for receiving a charge of magnetizable material, means for subjecting sad charge to heat, separate means for subjecting said magnetic' charge to a path of magnetic flux of which said charge forms a part, and means disposed in said path of magnetic flux for determinin the magnetic properties of said charge und er the variable effects of heat treatment-s thereof.

6. In combination, a furnace having a heating chamber, work to be heated located in said chamber, a source of electric energy, a. coil enclosing said chamber connected to said source to establish a magnetic field passing through said work, a source of heat independent of said source of energy, and a means responsive to changes in the voltage between two or more turns of said coil for indicating the condition :of said work.

'in coinhination, u furnsce having e heatin r hzirnher, work to he ii ed lo -eted in said ;ein a 'source of electric energy, a coil en- ;ul rhaoiher connected to said source .hlish e'nugetic field passing through seid work, a source of host independent of ce of energy comprising heating elerranged atije cent said Work and enerrn powe supply clrcut indegend 'aid irst nientioned source of electrc end means responsive to change in. nctive effects of said coil and connected'in eiectricai reiaticn 'to said coil for indiea tin'` he mrgnetic condition of said work hoat treatment furnace. a heating V ehanher for receiving a charge of rnagnetizole material, means 'for applying heat to said heat treatment chainber, a winding disposed nd said heat treatment chamher for suh- J ,V ng the n'agnetizable charge within said chan her to a inagnetic iun, and means connectedto selected turnsof said winding for indicating the magnetic permeability of said cherge.

9. ?in a heat treatment furnace, e heat treatment chamber for receiving a magnetizable charge, means for applying heat to said charge, e winding surrounding said heat treatment chamher for suhjecting said charge to e, inegnetic iiur; and circuits connected with selected turns of said winding for deterniining'the megnetic permeability of said charge. 4

10. In a heat treatment furnace, a heat treatment chamher for receivng a magnetizable charge, means for applying heat to the charge within said heat treatment chamher, a Winding surrounding said heat treatment chemher for suhjecting said charge to the passage of magnetic fiux and means connect ed to selected turns along said winding for indicating the rnagnetic permeability of said cherge throughoutthe process of heat treatment thereof.

ll. In an electric furnace, the combination with a heating chamberhaving` heating-elements therein, work to he heated located in said chanher, a source of electric current connected with said elements, means automatically responsive to changes in the chamber temperature for controlling the fiow of said current through said heating elements, a coil excited by an electrc current independently of said heating elements to establish a ,magnetic field through said work, a secondary coil in inductive relation with said first coil, and means responsive to changes in the inductive efiects of seid primary coil and connected in electrical relation with said second coil for indicating changes in the magnetic properties of the work in said chamber.

12. In a heat treatment furnace, a heet treatment chamber 'for receiving a magnetin able charge, a power source, electrical means connected with said power source for subjecting seid charge to heat, e megnetic system comprs ng a prin ery and secondary winding surrounding said heet treatment chemhei' tor establishing a path of magnetic iux through said magnetizable cherge, a devce for indi ceting the inagnetic permeabiiity of said cherge connected in circuit with said secondery windng, a contector disposed in series with said power source and seid electricel means, and a reiey system for controlling said contectorin accordance with the .temperature of the furnece i 13. In a heet treatment furnace, :i heet treatment chamber for receiving a nagnetizable cl arge, a power source, an electromae net constitutinga magnetic circuit disposed about said heat treatment chamher for establishing a path of magnetic lux passing through said magnetizahle charge, a meter connected with said electronagnet for indicating the magnetic properties of said charge, an electrical heater in said heat treatment chamber for subject-ing said charge to heat, circuit connections for supplying heating current from said power source to said electrical heater, a contactor disposed in series with said circuit 'connections and a relay system for controlling said contactor in accordance with the temperature of the furnace.

14. In combination, a furnace having a heating chamber, work to be heated located in said chamber, a source of electric current, a primary coil located adjacent to said chamher and excited by said current to produce a magnetic field passing through said work, a

sccondary coil having a current induced therein 'by said magnetic field, a meter responsive to changes in the inductive effects of said first coil connected in series with said second coil and a source of heat in said heating chamber indlependent of said primary and secondary co s.

In testimony whereof I aflix my signature WILLIAM B. COOLEY. 

